OregonBuys - Remaining Projects Summary~1.pdf

OWRD – Dam Safety Project Information & Update Version: February 9, 2022

This is not a solicitation but information on current and proposed Dam Safety Projects. This is not a complete list of projects. OWRD may add to or delete projects from this list. This document will be updated from time to time.

Project: Wageman Dam

RFP Anticipated Posting Date: mid-February

The purpose of this analysis contract is to fund an options evaluation that will inform decision making to address the issue with the conduit of Wageman Dam. The conduit through Wageman Dam is a thin walled steel pipe that dates to 1969 making the conduit more than fifty years old, well past the designed life.

The last time the conduit was operated, water was observed exiting the dam around the outside of the conduit. This indicates there are holes in the conduit. As a result, the conduit is no longer operated. In addition, the size of the conduit is insufficient so slip lining the conduit is not an option. The conduit needs to be replaced or an alternative means to drain the reservoir needs to be developed.

Dam Name NID# File# Latitude Longitude Height Storage Wageman OR00496 W-79 N43.10406112 W123.59004974 40 ft 50 ac-ft

Scope of Work

• Develop options to address the issue with the conduit

• Provide cost estimates for each option

• Site visit(s)

• Project management and meetings

Project: Mays Dam

The purpose of this analysis contract is to fund the analysis of the conduit for Mays Dam. Conduits through dams are key safety features used to drain reservoirs in the event of an emergency. The conduits of many dams in Oregon are made of corrugated metal. This type of material has a design life of 25-30 years. The conduit through Mays Dam is a corrugated metal pipe that dates to the 1950’s, making it more than 60 years old, well past the design life. Due to the age and unknown condition of the conduit, the conduit must be evaluated to determine the risk it may pose to the dam.

Dam Name NID# File# Latitude Longitude Height Storage Mays OR00355 M-37 N44.74959945 W120.506958 37 ft 457 ac-ft

Scope of Work

• Scope the full length and interior surface of the conduit

• Evaluate the integrity of the conduit

• Recommend repair or replacement of the conduit

• Estimate the remaining conduit life

• Site visit(s)

• Project management and meetings

Project: Morgan Lake Dam

The purpose of this contract is to fund a seismic analysis of Morgan Lake Dam. Morgan Lake Dam is located 2 miles west of and above the City of La Grande. In 2008, a Dam Breach Analysis was completed for the dam. The results of the analysis indicated that if the dam were to fail, approximately 24,000 cubic feet per second of water would flow down Deal Canyon. The resulting flood would cover the greater portion of the City, placing over 10,000 residents at risk. The embankment is either a hydraulic fill or fill compacted by animals and is close to a significant earthquake fault, one that has been active in the not too distant past. A seismic analysis is needed to develop a better understanding of the risk a seismic event poses to the dam.

Dam Name NID# File# Latitude Longitude Height Storage Morgan Lake

OR00653 M-64 N45.30485153 W118.13696289 23 ft 780 ac-ft

• Engineering geologic interpretation of subsurface conditions

• Evaluation of historical construction practices at dam, and construction as hydraulic fill or puddle compacted

• Determination of Maximum Credible Earthquake and dam site acceleration from Grand Ronde fault system

• Seismic Analysis (assessment level without drilling)

• Project Management and meetings

Project: Lower Pony Creek Dam

RFP Anticipated Posting Date: March

The purpose of this analysis contract is to complete the seismic vulnerability analysis and develop mitigation options for Lower Pony Creek Dam. The Coos Bay North Bend Water Board is the owner of this dam which is one of two sources of their municipal water supply. This dam is very close to the Cascadia Subduction Zone. The Lower Pony Creek Dam was not designed for a large earthquake. For this reason, the Department recommended the Water Board complete a seismic safety analysis of the dam. The Water Board paid $98,563 for a Phase 1 geotechnical investigation and preliminary analysis.

This Phase 1 analysis identified loose sand under the dam, with high potential for liquefaction which could cause catastrophic failure. Phase 1 did not include sufficient subsurface exploration for full determination of specific risk or mitigation alternatives. This is a very high-risk scenario, as there is a daytime population of about 690 people living or working in the inundation zone, as well as a water treatment plant right below the dam. Dam failure would cause catastrophic loss of life because there would be no significant warning. Dam failure would also destroy the municipal water supply for both Cities.

Dam Name NID# File# Latitude Longitude Height Storage Lower Pony Creek

OR00070

P-6 N43.37899017 W124.24208831 32 ft 400 ac-ft

• Project Management/Meetings

• Subsurface Investigation

• Laboratory Testing (index testing and cyclic testing)

• Liquefaction Analyses & Residual Strength Analyses

• Finite-Element Deformation Analyses

Project: Inundation Analysis Package 1 & Package 2

RFP Anticipated Posting Date: March

This contract will fund dam breach inundation analyses for 16 State regulated dams. The 16 dams will be separated into 2 packages of 8 dams each and a separate RFP will be posted to OregonBuys for each package. This information will be used by the Oregon Water Resources Department (OWRD), Dam Safety Program to assess the current hazard rating of these dams. The Dam Safety Program classifies dams into one of three hazard ratings based on the potential for loss of life and/or damage to property should a dam fail. The hazard ratings, as described by Oregon Administrative Rule (OAR) 690-020-0100, are: High, Significant, and Low.

Prior to 2009, there were no Administrative Rules in place that formalized the hazard rating process. As a result, most of the hazard ratings were based on professional engineering judgment. In addition, most of Oregon’s 950 state regulated dams were built prior to 1976. Consequently, land use downstream of many of these dams has changed since the dams were first constructed. The Dam Safety Program has identified 15 dams in which the risk to life is greater than originally anticipated when the hazard ratings were first set. Changing the hazard rating from Low or Significant hazard to High hazard will allow the Dam Safety Program to prioritize resources and take action on dams that pose an inherent risk to life.

The current Dam Safety Administrative Rules stipulate that a hazard rating can only be set or changed using the results of a dam breach inundation analysis. Therefore, this contract will fund dam breach inundation analyses to re-evaluate the hazard ratings for dams that may pose a greater risk to life than their current hazard rating suggests. Results of the analysis must be provided in the form of an inundation map and summary report. The maps produced by the contractors will be used by the OWRD dam safety program, to verify or change hazard rating of dams regulated by OWRD. The maps may also be used for emergency planning, mostly for dams determined to have a significant hazard classification.

1) Develop a dam breach inundation model using HEC-RAS for each of the 15 dams in this contract.

The model can be developed as a 1D, 2D, or combined 1D/2D. All models must extend downstream of the dam until there are no structures impacted by the breach flow. In addition, all models must be extended downstream sufficiently far enough to ensure that the downstream boundary condition does not introduce error at the downstream most area of concern.

2) All dam breach inundation models should be deterministic in nature unless otherwise noted

3) There will be one model per package that must be stochastic in nature. The stochasticity should be developed by varying the dam breach parameters within certain ranges. The breach parameter ranges will be provided by OWRD. The results of the stochastic analysis should be presented in a probabilistic inundation map showing the 99%, 95%, 90%, 75%, and 50% exceedance probability inundation boundaries.

4) The average 0.2% AEP must be used as the inflow to all models unless otherwise noted.

5) Breach initiation must occur at maximum reservoir stage resulting from the 0.2% AEP inflow. If the dam is overtopped by 0.2% AEP inflow, then breach initiation should occur at the reservoir stage corresponding to the top of dam elevation.

6) The analysis must be developed using LiDAR.

7) The dam height and storage should be taken from the approved as-built or design drawings.

Where drawings do not exist, the height and storage from the OWRD dam safety database can be used but should be checked for accuracy using LiDAR.

8) Field work is not required

9) A sensitivity analysis must be performed. The sensitivity analysis must, at a minimum, be conducted on the following model parameters: Manning’s Roughness Coefficient, computation interval, and breach flow parameters (breach width, failure time & side slopes).

Note: This notice is to inform interested consultants of potential OWRD projects in the pipeline. OWRD reserves the right to move any of the projects to solicitation and eventual award or cancel any of the projects at its discretion.